JERUSALEM — An Israeli security official said Thursday the Hamas militant group has been holding an Israeli citizen in the Gaza Strip for nearly a year.

The official said the Israeli of Ethiopian origin ran past the border fence into the Gaza Strip last September, nearly two weeks after the end of the Israel-Gaza war, and has been held by Hamas since.

The official said it is unclear why he entered Gaza. The official said Israel does not consider the Israeli to be a captive, and that Israel was treating the matter as a humanitarian issue. The official spoke on condition of anonymity because he was not authorized to speak publicly about the matter.

A spokesman for Hamas, Salah Bardawil, declined comment. “We don’t have any information about it. Even if is true, we don’t have instructions to talk about it,” he said.

Israel’s military lifted a gag order Thursday to reveal details of the matter. It is unclear why it decided to publicize the issue months after the incident. Israeli officials declined immediate comment.

According to Israeli media, Ethiopian-Israeli Avraham Mengisto, 28, arrived at an Israeli beach on the Gaza border the evening of Sept. 7, left behind his bag and crossed into Gaza through a breach in the border fence apparently left from movement of Israeli tanks during the war. Mengisto is from the city of Ashkelon, Israeli media reported.

Israeli Channel 2 TV said Prime Minister Benjamin Netanyahu had been in touch with Mengisto’s parents and that Lior Lotan, a retired Israeli army colonel, was handling negotiations to return Mengisto to Israel. The family had been instructed not to speak publicly about the matter, media said, but that news of Mengisto being held in Gaza had spread through Israel’s Ethiopian immigrant community.

Israeli Channel 10 broadcast an interview with a man it identified as Mengisto’s father, holding up a statement critical of Israeli authorities.